Changes in facial morphology in Macaca mulatta: a cephalometric study from 1.5 to 5 years of age

A cross-sectional and longitudinal (3.5 years) study on the craniofacial growth of 10 male rhesus monkeys, using metallic implants and a radiographic cephalometric technique based mainly on angular measurements, led to the following observations. (1) Maxilla and mandible were displaced in a forward and downward direction during growth, the sagittal changes being predominant over the vertical changes. (2) Maxillary and mandibular prognathism increased continuously during the whole time span. This increase was twice as great for the maxilla as for the mandible. (3) The inclination of the palatal plane and the mandibular plane changed very little over time. (4) Mandibular form remained constant, but the cranial base showed a significant flattening between approximately 1.5 and approximately 3 years of age. (5) Upper and lower occlusal plane angles changed little over time. (6) The interincisal angle decreased significantly until approximately 3 years of age in relation to the increase in proclination of the permanent incisors in the maxilla and mandible. The intermolar angle remained fairly constant. Changes in some of the variables reported (maxillary and mandibular prognathism, sagittal jaw relationship, mandibular length, interincisal angle, proclination of the upper and lower incisors, and opening of the cranial base angle) occurred as a function of age. The use of angular measurements allowed us to develop a series of templates that will provide a useful tool for a quick check of normal craniofacial morphology at three representative time points.